Immune response to HBV in Patients
Adam J. Gehring, Ph.D.Biology Lead
Toronto Centre for Liver DiseaseUniversity Health Network (UHN)
Assistant ProfessorDepartment of Immunology
University of Toronto
Adaptive Immune Response to HBV
Acute/ResolvedRobust, coordinated adaptive immunity1. CD8 T cells mediate clearance of infected cells2. B cells - anti-HBs marker of resolution 3. CD4 T helper cells support CD8 & B cells
ChronicWeak Adaptive Immune response1. Low T cell frequency2. Lack of effective antibodies
X XX
T
T
TT
T
B B
T cell responses do not correlate with clinical stages• Arbitrary definitions and many patients = indeterminate
Profile of the HBV-specific T cell Response in Chronic HBV
Park 2015 Dec;150(3):684–5.Kennedy Gastroenterology. 2012 Sep;143(3):637–45.
Age may be better correlation of T cell immunity• Higher T cell frequency detectable in younger patients• Lower PD-1 expression
T cell PD-1
Pallett, J. Exp Med. 2017 Jun 5;214(6):1567–80. Tan J. Virol. 2008 Oct 24;82(22):10986–97.
Variation in T cell repertoire• Age of patients alters antigen-specific repertoire• Different Genotypes/HLA profiles elicit different T cell repertoires• Important for measuring immunity• Designing vaccines
Profile of the HBV-specific T cell Response in Chronic HBV
T cells in the liver do not equal T cells in the blood• Different phenotype• Different functional profile• Different transcription factor profile
Total T cells HBV-specific T cells
Blood
Liver
Patients who lose HBsAg have higher T cell frequency• HBsAg loss on nuc treatment shows T cell recovery
• almost to level of acute response• T cell response in spontaneous clearance is higher than untreated• Cross-sectional study – chicken & egg?
Profile of the HBV-specific T cell Response in Chronic HBV
Boni, Gastroenterology. 2012 Oct;143(4):963–9.
Hepatotropic virus Liver is generally a tolerizing organ
o Hepatocyte/LSEC Antigen presentation = bad for primingo Suppressive Dendritic cellso High IL-10, TGF-β, PD-L1, enzymes degrading essential amino
acids, hypoxia
Hepatitis B Virus Immune Evasion/Exhaustion
High Antigen burdenHigh viral load High viral antigen
HBsAg up to 1 mg/ml in serumHBc-related Ag = ?
Constant presentation?Hepatocytes, LSEC, Periphery?
Inhibitory receptors often co-expresseda. Nebbia, PLoS ONE 2012; 7: e47648. b. Boni, J Virol 2007; 81: 4215–4225. c. Schurich Hepatology. 2011; 53: 1494–1503d. Bengsch, J. Hepatol. 2014 Dec;61(6):1212–9e. Fisicaro Gastroenterology. 2010 Feb;138(2):682–93
Significant mitochondrial dysfunction• Impairs T cell functionality• Antioxidants restore T cell functionality
a. Fisicaro Nat Med. 2017 Feb 6;23(3):327–36.
Active elimination of T cellsActivation induced apoptosis
a. Lopes J. Clin. Invest. 2008 May 1;118(5):1835–45
NK-TRAIL mediated killing of T cellsa. Peppa J. Exp Med. 210, 99–114 (2013).
Specific Mechanisms Suppressing HBV-specific T cells
Non-specific Mechanisms Suppressing HBV-specific T cell Function in chronic HBV
Arginase elevated in HBV patients• Correlates with ALT level• Suppresses T cell proliferation & function
a. Sandalova. Gastro. 2012 Jul;143(1):78–87.e3.b. Das. J. Exp Med. 2008 Aug 11;205(9):2111–24
Myeloid Derived Suppressor Cells (MDSC)• Produce Arginase and IL-10• Suppress T cell expansion
a. Pallett, Nat Med. 2015 Jun;21(6):591–600.
Regulatory cells – Treg & Breg• frequency correlates with ALT• produce IL-10• Depletion in vitro can enhance CD8 expansion
a. Das, J. Immunol. 2012 Oct 4;189(8):3925–35b. Xu, J. Immunol. 2006 Jul 1;177(1):739–47
Tregs Bregs
Acute/ResolvedRobust, coordinated adaptive immunity1. CD8 T cells mediate clearance of infected cells2. B cells - anti-HBs marker of resolution 3. CD4 T helper cells support CD8 & B cells
ChronicWeak Adaptive Immune response1. Low T cell frequency2. Lack of effective antibodies
X XX
T
T
TT
T
B B
Adaptive Immune Response to HBV- What About B Cells? -
Bertoletti, J. Hepatol. 2016 Apr;64(1 Suppl):S71–83. Rehermann, Nature Medicine 19, 859–868 (2013)
Adaptive Immune Response to HBV- What About B Cells? -
Detection of the HBV antibody response• Antigen > Immune Complexes > anti-HBs• Immune complexes found in >90% of acute patients• memory anti-HBs-specific B cells detectable by elispot
• after resolution• after vaccination
Madaliński, Clin & Exp Immun, 1979 Jun;36(3):371–8. Pernice, Clin & Exp Immun, 1979 Aug;37(2):376–80. Böcher, Hepatology, 2000 Feb 1;31(2):480–7. Vanwolleghem, Hepatology. 2015 Jul;62(1):87–100.
Memory anti-HBs-specific B cells difficult to detect • Fewer immune complexes in chronic patients
• mainly patients with active disease• Correlates with activated B cell profile in patients with
active disease • IgG subclasses may be associated with better control
B
Activated
Dusheiko, J. Clin. Invest. 1983 May;71(5):1104–13. Barnaba, Clin & Exp Immun. 1985 May;60(2):259–66. Böcher, Clin & Exp Immun,1996 Jul 1;105(1):52–8.
Oliviero, J. Hepatol. 2011 Jul;55(1):53–60.Rath, Clin & Expl Immun. 1988 Apr;72(1):164–7Gregorek, J. Hepatol. 2005 Apr;42(4):486–90.
Complexity of the Innate Immune Response to HBV
Arguably more complex than the T cell responseCD4 CD8NK
γδ T cell
MAIT
MN/MO
DC
Innate effectors• NK cells, MAIT cells, γδ T cells• Innate effectors can be negative regulators in chronic HBV patients• Little data on their role in recognizing/eliminating infected hepatocytes
Myeloid Cells• Dendritic Cells, Monocytes, Macrophages• Antigen presentation• Cytokine production
Parenchymal cell responses • Hepatocytes, Endothelial Cells, Stellate cells
Human innate immune response studied mainly in context of pathogenesis of chronic HBV• Limited data comparing innate immunity in acute - resolved – chronic HBV patients
Innate Immune Response in Chronic HBV
Vertical transmission accounts for a majority of chronically infected patients
No acute response to HBV because virus is always present • Innate immune system is exposed to HBV before birth
Hong. Nat Comms 6, 1–12 (2015).
NK cell IFN-γ production suppressed• Related to IL-10• Especially in hepatitis patients
Peppa, PLoS Pathog. 2010 Dec 16;6(12):e1001227.
Gehring J Clin Invest. 2013 Sep 3;123(9):3766-76 Boltjes PLoS ONE. 2014;9(5):e97006.
Myeloid cell function in chronic HBVDendritic cell • function highly variable• Inhibited, activated, restored with nucleoside analogues
Monocytes• Contain HBsAg in vivo• No evidence of altered stimulatory capacity • Intact cytokine production
TNF-α
Alterations in the Innate Immune Response to HBV
Caveats of myeloid cell analysis• Short-lived compared to T & B cells• Spend few days in circulation
• Susceptible to environmental changes• Bone marrow alteration?
Dapi HBsAg
Innate cells dominate the immune composition of the liver
Innate Immune Response in Chronic HBV
(NK/γδ/MAIT)
Lymphocytes
Blood
(NK/γδ/MAIT)Liver Liver
Myeloid Cells
Blood
Pattern Recognition receptors
Phase I/II Clinical Trials• TLR-7• TLR-8• Rig-I
Pre-clinical• STING• Inactivated viruses (PPOV)
Innate Targets for Immunomodulatory Drug Development
Induce innate/antiviral cytokine production• Cytokines: IL-1α, IL-1β, IL-10, IL-6, IL-12, IL-18, TNF-α, IFN-α, IFN-λ• Chemokines: CXCL-8, -9, -10, Mip1a, Mip1B, MCP-1
Gehring, Best Pract Res Clin Gastroenterol. 2017 Jun;31(3):337-345
Summary
HBV-Specific T cell response• Not significantly different across different phases of HBV• Repertoire varies by genotype, HLA profile and localization• Multiple specific and non-specific mechanisms maintaining the exhausted state
B cell response• Top level data – more work is needed• Memory B cells are detectable in resolved/vaccinated• So far, difficult to detect in chronic patients – need better tools• activated profile during active disease: meaning?
Innate Immunity• Needed to enhance T cell immunity = antigen presentation• Significant antiviral potential if properly harnessed• Reduced NK cell function in chronic HBV• Negatively regulates T cell immunity = MDSC, NK-TRAIL